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CC1101 - communication distance is poor / antenna matching

Maciej Fajfer
Intellectual 330 points
Other Parts Discussed in Thread: CC1101

I have access point and some sensors both based on CC1101. I would like to ask about W3127 antenna matching to CC1101. It's helical antenna from Pulse Electronics. Here is my CC1101 section in sensor:

CC1101 section is based on SWRR046A reference design and W3127 section is based on SWRR070 reference design (including PCB layout). Below is my own PCB layout:

Range is very poor. It's estimated 15 meters. I think antenna matching circuit is wrong. I just complete together both reference designs. Maybe I should delete C21, C23 and then insert short wire instead of C23 ? Incorrect PCB layout ? I haven't network analyzer.

  • 0
    TI__Guru**** 317180 points
    The antenna match is dependent on:
    - The size of the ground plane
    - Near field. Typically the type of casing or objects placed close to the antenna.

    If you have changed something compared to the antenna DK you probably have to retune the antenna.

    Without a network analyzer you can do a frequency sweep and read the RSSI. The highest RSSI will mean the resonance frequency.
  • 0 in reply to TER
    Intellectual 330 points

    Thank you for your response. Casing change something. Without it range is 20 m but inside plastic casing its 15 m. In my project I use GFSK modulation, 4.8 kbps baud and +10 dBm power out in sensors and access point. In my design I use WOR. I can read RSSI in other CC1101 or I can even use simple high frequency detector with sensitive voltmeter but frequency sweep will be better.


    What is your opinion about PI filter L3, C18, L4, C21 and C23 in such case ? Should I change something in this section ? Should I perform retune by C10 and L5 ?

  • 0 in reply to Maciej Fajfer
    TI__Guru**** 317180 points
    You should use C10 and L5 for tuning.